The present disclosure relates to a method of producing a weight-optimized pneumatic tire rim as well as to a device for implementing the method.
For producing a pneumatic tire rim, it is known, for example, from German Patent Document DE-OS 26 47 464 to reduce the thickness of the outlet wall and that of the tube section, while simultaneously extending the length, on a longitudinally welded cylindrical tube section, which is also called a tire. This is done by pressing on at least one rotating pressure roller or drawing roller in correspondence with a tool lining, which results in partially different wall thicknesses over rotational symmetrical areas and-which wall thicknesses are defined by the function.
Thus, normally, the rim dish is welded together with the rim well in the area of a well base, for which the latter has to have a certain wall thickness.
Because of required weight optimizations, the areas which, in contrast to the above-mentioned welding area, are subject to no special stress, should be constructed as thin as possible. That is so that the original wall thickness, in the case of the finished pneumatic tire rim, exists only in the above-mentioned stressed areas, and is correspondingly reduced by extrusion molding.
However, this is connected with a number of problems. Thus, for example, several working steps are required for achieving the reduction of the wall thickness, which leads to relatively high manufacturing times and resulting high manufacturing costs.
In this case, it is a contributing factor that the edges of the flanks become “uneven” as a result of the extrusion or the drawing of the material. That is, an edge is created which, in the broadest sense, is frayed and requires a finishing.
Particularly in view of the fact that such pneumatic tire rims are produced as serial products in large piece numbers, the above-mentioned problems have a special significance.
The present disclosure relates to a method of producing a pneumatic tire rim such that manufacturing times are shortened and a more cost-effective manufacturing therefore becomes possible.
Thus, the present disclosure includes a method of producing a weight-optimized pneumatic tire rim having rotationally-symmetrically partially different wall thickness. The steps include: providing a tube section having a first wall thickness and two end sides; leveling the first wall thickness starting from the two end sides over a defined rotationally-symmetrical area thereby forming two flanks by precontouring, each of the flanks having a second wall thickness, and pushing tolerance-caused excess material of the flanks into a well base zone between the two flanks: and contouring the flanks by pressure rolling while drawing each of the flanks toward an end area of each of the flanks and reducing the thickness of each of the flanks partially differently to predetermined measurements. The present disclosure also includes a device including a tool lining having one or more of a precontour and a contour, the tool lining having a first lining part and a second lining part, which lining parts are movable relative to one another in an axial direction.
As a result of known manufacturing processes, the tube section used as a blank has relatively large tolerances in its wall thickness which, during the extrusion to a defined wall thickness of the flanks, may lead to unevenness of the edges.
In accordance with the present disclosure, an exact predefinable material volume is created which is available for further machining of the flanks, including longitudinal drawing, contouring and bringing to a predefined wall thicknesses.
The longitudinal drawing, which is the result of possible partial reduction of the wall thickness carried out by pressure rollers, is limited by a stop which is provided in a surrounding manner at a surface area of the tool lining and on which the respective flank rest in an end position, after termination of the pressure rolling.
By the volume of the flanks, which is present in a defined manner after the pressure rolling, the length of the flanks after the termination of the deformation can also be determined while taking into account the desired wall thicknesses.
This allows not only a production of the rim well which is as precise as possible with respect to desired measurements, but subsequent trimming of the edges can also be eliminated because, in the case of each rim well to be produced as a serial product, the same flank volumes exist after the first process step.
The excess material, which results from the thickness tolerances, is pushed into the well base zone during the leveling of the wall thickness, where it leads to a thickening of the wall.
Thus, as the initial wall thickness of the tube section, a wall thickness can be selected which is less than the end wall thickness in the area of the well base zone whose end thickness is, in turn, obtained from the original wall thickness and the added tolerance material of the flanks.
According to an embodiment of the present disclosure, it is provided that, before the leveling of the wall thickness of the then still cylindrical wall section as an initial product, the cylindrical wall section is widened on one or more of the end sides.
In this case, the diameter of the cylindrical tube section is smaller than the largest outside diameter of the rim well to be produced by the subsequent machining steps, whereas the diameter of the tube section corresponds to the largest diameter of the rim well when the end-side widening is terminated.
Since the material volume remains the same in each embodiment, in the case of a smaller diameter of the tube section, a larger width or wall thickness of the tube section is provided.
The above-mentioned widening of the tube section has manufacturing-related advantages since, during the subsequent pressing for the contouring, an uncontrolled excursion of the end areas is prevented.
A device for implementing the above-described method is constructed such that, for receiving the cylindrical tube section, a two-part tool lining is provided. The tool lining is contoured at its outer surface area, the two tool lining parts being axially movable relative to one another.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.